Soil-Geosynthetic Interface Shear in Different Testing Scales

Geosynthetics have been used to improve mechanical performance of roadway layers (e.g., geosynthetic-reinforced asphalt, geosynthetic-stabilized bases) and a wide range of transportation infrastructures (e.g., geosynthetic-reinforced soil walls). A key aspect in understanding soil-geosynthetic interaction mechanisms involved in each application includes characterization of the interface between geosynthetics and adjacent materials. This study evaluates soil-geosynthetic interface shear in various pullout test scales including standard, smaller than standard, and larger than standard scales. Experimental results obtained from tests conducted in each scale were analyzed to determine the soil-geosynthetic interface shear model. An iteration procedure, similar to that used in t-z analysis of pile loading, was developed to simulate incremental geosynthetic movements. Shape and parameters of the interface shear model were changed to minimize the residual error between experimental and simulated data. It was found that mobilization of the interface shear in the small-scale test differs from that in the standard- and large-scale tests. In the standard- and large-scale tests, the ultimate soil-geosynthetic interface shear mobilized at comparatively small displacements, which could be represented by a linear plastic interface shear model. In the small-scale test, however, the interface shear developed in two phases. A portion of the ultimate interface shear mobilized at comparatively small displacements while additional resistance continued to mobilize at extended displacements. Consequently, the development of interface shear resistance in the standard- and large-scale tests was found to depend on progressive increase of the geosynthetic mobilized length, whereas in the small-scale test the interface shear resistance developed by displacement of the entire geosynthetic.